150k spare a year, diligently invested 20 years with an overall real return rate of 5% (which should be relatively achievable with index funds, otherwise our capitalist machine is in serious trouble and it won't matter too much what my portfolio does) compound to $5.2M. And that's a real return rate so it should be protected against inflation (add a ~3% if you want to do pre-inflation calculation and see the number skyrocket to ~$7M).
In fact, that's what I've been doing myself, and I am just on track at ~Y8 like I said in my other comment, all while being an average productive software engineer in the bay. The key is to live frugally and invest in a very diversified way.
I live frugally in the bay area with ~$40k/y, I don't succumb to peer pressure of having fancy houses and cars, so for me saving ~150k/y (a bit less actually) is rather easy, and I'm lucky enough to be in a relationship with a woman who feels the exact same, and my life couldn't be any fuller: I'm not slave to material possessions, I live in a decent apartment close to work, my weekends are full of nice outdoor experiences, I work on world-class technology in the bay, and I'm building some serious wealth in the process so I can gain absolute freedom in early/mid 40s (hopefully).
I should also say, for full disclosure, that I don't plan on having kids (I have a huge extended family with tons of nephews, so that's enough for me), and I might just adopt much later in life if I'll feel the need, so that might heavily affect my savings numbers.
Math:
- Y1: $157,500.00
- Y2: $322,875.00
- Y3: $496,518.75
- Y4: $678,844.69
- Y5: $870,286.92
- Y6: $1,071,301.27
- Y7: $1,282,366.33
- Y8: $1,503,984.65
- Y9: $1,736,683.88
- Y10: $1,981,018.07
- Y11: $2,237,568.98
- Y12: $2,506,947.43
- Y13: $2,789,794.80
- Y14: $3,086,784.54
- Y15: $3,398,623.77
- Y16: $3,726,054.95
- Y17: $4,069,857.70
- Y18: $4,430,850.59
- Y19: $4,809,893.12
- Y20: $5,207,887.77